Composition for treating nodular iron



Aug. 30, 1955 E. E. ENSIGN 2,716,602

COMPOSITION FOR TREATING NODULAR IRON Filed May 11, 1951 E7 5. E NS G N INVENTOR.

ATTORNEYS Uteri;

COMPOSITION FOR TREATING NODULAR IRON Application May 11, 1951, Serial No. 225,853 4 Claims. (C1. 75-43 This application is concerned with the founding industry and more particularly with a method for improving the physical properties of nodular cast iron. This so-called nodular iron has received recent widespread publicity both in the current and patent literature and it is thought to be unnecessary to describe it further other than to state that it may be produced by adding sufficient magnesium to an appropriate gray iron melt to produce a magnesium residual of about 0.05% and inoculating the melt just prior to pouring into the mold with any of the many commercially available graphitizing inoculants. This treatment, if properly carried out, will result in an as cast product in which the uncombined carbon is present in the form of spherulites or nodules rather than the flaky form which is characteristic of typical gray iron. The matrix may be either ferritic or pearlitic, depending upon the analysis and casting conditions. As is now well understood in the art, the absence of flaky graphite permits the production of a casting having :1 much higher tensile strength and ductility than ordinary gray iron.

The production of nodular iron castings particularly in highly irregular shapes has been impeded by the persistant occurrence of a phenomenon referred to in the industry as cope defects. This name has been applied because of the tendency of this defect to occur at the upper portion of the castings. A casting seriously weakened by these cope defects may present to the eye a perfect surface and also appear radiographically sound.

However, when fractured the castings will exhibit a large number of inclusions of unknown composition. While the exact composition of these inclusions is un known, it is apparent that a large amount of graphite is included in their makeup. in a fracture, these inclusions are disclosed as planes of discontinuity varying in size from those barely visible to the naked eye up to one quarter of an inch in diameter. These graphite laden planes of discontinuity, of course, seriously weaken the castings.

These inclusions have been found particularly troublesome in the casting of crankshafts for internal combustion engines inasmuch as they tend to congregate at the juncture of the pin bearing and check, which is precisely the location of maximum stress concentration at which fatigue cracks tends to develop.

It has been discovered that this phenomenon of cope defects can be substantially eliminated by the applica tion to the molten metal of any of the many fluxes which have been developed for use with magnesium.

Particularly good results have been obtained with boric acid, borax, fused borax, and alkali metal fluoborates, as well as the fluxes which are based upon the double chloride of an alkali metal and magnesium. For a detailed description of commercially available fluxes, reference is made to the Metals Handbook, 1948 edition, page 974.

While the inventor has not completely developed the theory underlying his invention, it is his belief that oxidizing gases preferentially oxidize the magnesium content of the magnesium containing iron and that the resultant highly refractory magnesitun oxide is responsible for the occurrence of cope defects.

To eliminate these cope defects, the inventor intimately contacts the magnesium type of flux with the molten magnesium containing iron. A particularly economical and satisfactory method of applying these magnesium type fluxes to the molten metal is the contacting of the molten metal with a porous refractory body which has beenimpregnated with the magnesium flux.

In the application of this process, the inventor has been singularly successful in the production of an internal combustion engine crankshaft having the following composition: t

Percent Carbon 3.50-3.80 Silicon 2.203.00 Manganese 0304.00. Phosphorus 0.100 Sulphur 0.017 Magnesium 0.050 Iron Remainder The particularly preferred form of refractory is shown in the drawing in which Figure 1 is a plan view of the refractory and Figure 2 is a sectional View of the refractory taken along the line 22 in Figure 1.

As can be readily seen from the drawings the refractory t'orm comprises a body which is circular as seen in the plan view and in section is isocles trapezoid. A number of holes are provided in this form. The axes of these holes are parallel to the axis of the body. It is understood that this body is impregnated with a mag nesium type flux. This refractory is incorporated in the mold in such a way that all of the metal which will eventually become a part of the finished casting must pass through the holes in the refractory body. The passage of the molten metal through the relatively large number of holes causes a sufficiently intimate contact between the flux and the molten metal to result in the substantially complete elimination of the cope defects.

It is disclosed in copending application Serial No. 189,133 filed October 9, 1950 in the name of Gosta Vennerholm and Royal A. VanPatten that refractory bodies of this type may be prepared by dipping the fired body in molten magnesium type flux and relying upon the flux adhering to the refractory. This practice has been employed extensively by the assignee of this invention and has been found to give satisfactory results. However, difficulties have been encountered in securing a uniform coating by the dipping procedure. The particular structure mentioned also has been unsatisfactory in that it is necessary that the coated refractory bodies be protected from the atmosphere prior to use due to the deliquescent nature of the magnesium fluxes.

It has been found that a more satisfactory refractory body may be prepared from a porous body of sand bonded by a cured or partially cured phenol formaldehyde type resin. This porous body is prepared so that it contains up to 15% or more and preferably about 10% by weight of a magnesium type flux. This body is prepared by admixing the sand, uncured phenol formaldehyde resin and magnesium type flux in the dry state. Suflicient phenol formaldehyde resin is added to give the requisite strength. Ordinarily this will amount to from 3% to 10% by weight of the resin. A metal mold appropriately shaped to produce the article shown in Figures 1 and 2 is prepared and the mixture of sand, flux, and resin added. This addition is preferably made with the mold heated although this is not necessary. In any event the mold with the contained mixture is heated sufiiciently to cure the sand flux resin mixture to the desired extent. A cure time of one minute with a metal temperature of about 350 Fahrenheit has been found to be adequate. A typical composition which has been found satisfactory is:

Percent Resin 5 Magnesium type flux No. 90 A. F. A. sand 85 drawings has been found to be highly satifactory for applying the magnesium type flux to the molten metal, the invention is by no means so limited. A refractory body impregnated with magnesium flux may be incorporated in the mold and located so that the metal enter ing the mold will flow across the refractory body.

I claim as my invention:

1. A refractory body comprising a porous body of finely divided refractory particles bonded together with an at least partially cured phenolic type resin and carrying a magnesium type flux.

2. A refractory body comprising a porous body of finely divided refractory particles bonded together by an at least partially cured phenolic type resin and carrying a magnesium type flux and a waterproofing agent.

3. A refractory body comprising a porous body of sand bonded together by an at least partially cured phenolic type resin and carrying a magnesium type flux and a waterproofing agent.

4. A refractory article comprising a body coated with a waterproofing agent and comprising sand 92% to an at least partially cured phenol type resin 3% to 10%, magnesium type flux 5% to. 15%.

References Cited in the file of this patent UNITED STATES PATENTS Donelson et al. June 13, 1944 

3. A REFRACTORY BODY COMPRISING A POROUS BODY OF SAND BONDED TOGETHER BY AN AT LEAST PARTIALLY CURED PHENOLIC TYPE RESIN AND CARRYING A MAGNESIUM TYPE FLUX AND A WATERPROOFING AGENT. 